4 rules for parents of adult children living at home

If you don't already have adult children living at home, there's a good chance one of them will stay under your roof again at some point.

A Pew Research survey found 39% of adults ages 18 to 34 say they either lived with their parents at the time of the survey or had returned home temporarily in recent years.

You'll want to lend a hand if your child asks to move back in. But doing so without some ground rules could lead to problems for both of you.

Before you open your doors, consider our 4 smart moves to make if your adult child asks to move in with mom and dad.

Smart move 1.Set a deadline.

It's hard to deny that many recent college graduates have it hard.

Unemployment remains stubbornly high, and college graduates are leaving school with more than $26,000 in student loan debt on average.

Even if your son or daughter finds a job, rent, food and transportation costs can gobble up most of a recent grad's starting salary.

Welcoming them home for a bit is fine, but don't do it without setting a deadline for when your child will move out.

Steve Lewit, CEO and founder of Wealth Financial Group in Buffalo Grove, Ill., recommends you put it writing.

Let them stay for a year or until they pay off their student loans. Or tell them they can live at home for three months after finding that first job.

Every situation is different, but Lewit says what's important is establishing a defined conclusion.

"If the parent isn't clear on everything from the start, (the child) could end up being there a very long time," Lewit says. "You need an agreement at the beginning."

Smart move 2.Charge your child rent.

Charging rent isn't about you getting paid. It's about teaching your child to be responsible.

Even if you demand something nominal — say $100 per month — charging rent gets them in the habit of paying to keep a roof over their head and lets them know there are no free rides in life.

It also helps reinforce the understanding that it's not their house.

What's more, you might actually need some of that money.

Having another adult in your house will increase your expenses, from groceries to utility bills.

If you don't need the money, one option may be to tuck the monthly rent away in a savings account, then return it when your child gets that first apartment.

Say your child pays you $200 a month for 18 months. When he or she moves out, you could hand over a check for $3,600 to be used for a deposit and a couple months' rent.

Smart move 3.Keep tabs on finances.

Ordinarily, your adult child's finances aren't really your business.

But when you're offering a place to live, how he or she manages money is your business.

"You have the right to ask how they're spending their money if you're supporting them," Lewit says. "You need to ensure they're moving towards their goal. That's a part of the deal."

If your child is unemployed, you need to be certain he or she is working to find a job.

If they're staying at home to save or pay down debt, you need to know that's what's happening.

Have them show you a statement once a month to demonstrate they're paying down debt or saving money.

Keeping tabs will help keep your child on track. It could also help your son or daughter learn about budgeting and setting goals, says Adam Koos founder and president of Libertas Wealth Management in Dublin, Ohio.

While you're monitoring your child's finances, you might be tempted to help them along.

Don't.

"Don't give them gas money, fun money or anything else," Koos says. "If you give them more than the (bare essentials), you could be enabling them."

Smart move 4.Force financial independence.

Many parents struggle when it's time to cut off their children, but Lewit says at some point they need to be left to "just go figure it out."

Remember that deadline for moving out you set? Stick with it — even if the hope of your child's dream job has to give way to reality.

"They still need to find a job," Lewit says. "Something to make some kind of money. You have to draw a line in the sand or they could be there forever."

Further, your child may have to live with the prospect of high rent, big loan payments and low wages for a while.

They'll have to find some way to make it without you.

Allowing them to live at home indefinitely isn't doing them any favors. Supplementing their income isn't helping either.

They'll have to manage themselves at some point because you won't be around forever.